What computer peripherals need to be connected to the internal power source?

I had to shave the subject for space. What I mean is: What internally installed computer peripherals typically need to be connected to the internal power source? In my current system, I know all my drives (hard, floppy, cd) are connected to the power source, but not the video card, sound card, etc.

I ask because I am going to be buying a new system. I am not sure whether to get the default tower configuration with the 250 watt power supply, or a slightly more expensive one with a 300 watt supply.

For the record, the system is going to be packaged with a CD-RW drive, hard drive, integrated sound and video, an ethernet adapter, and modem. I will be adding my own monitor, keyboard, mouse, floppy disk drive, 2nd hard drive, scanner, and printer, and in the future, a G.Lite ADSL modem, possibly a third hard drive, a DVD-Rom or DVD-Ram drive, a tv capture card such as the ATI All-In-Wonder, a joystick, and a pc video camera.

I know that scanners, printers and monitors can be plugged in at an outlet. Mice, keyboards and joysticks don’t need a power source. I am sure the DVD drive and hypothetical third HD will. I am uncertain about the All-In-Wonder, the video camera, and the ADSL modem.

Would a 250 watt power supply be enough for all this stuff? Or would I have to make something external?

Go for the 300 watter. Especially if you’re going to go with an athlon - they don’t even run consistently on 250w. But it’s always a good idea to go with the 300.

I got an Athlon, the voltage requirments on the manual specify 200 watts. Anyway buy 300 watts & get a big case. You need a lot of drive bays for all that stuff.

Actually, I am getting a 750 mhz Duron on a “PC266 SiS 730S chipset mainboard…(with) Socket-A Processor Support”

The system specs on the site don’t say how much power this board uses, but that is an issue I hadn’t considered. I will ask them that in an email.

Actually, pretty much everything you plug into a computer requires a power source - the video card, modem, mouse, etc. The thing is that unlike the hard drive and CD-ROM drive, there is no separate power plug. For the cards, it’s taken care of in the PCI/AGP ports. For the peripherals (mouse/keyboard), it’s in the plug.

So the more stuff you tack on, the more power you’re using. That said, the mouse isn’t exactly a big drain on power. The important things are the CPU and drives.

Good God! My little PowerPC can keep up, AND uses less than 20 watts!

Transistors switching draw power, more transistors equals more power drawn, so if you want to impress us with your computer’s power, you need to tell us that it takes LOTS of watts, not less.

A measly 20 watts? Feh. Must not be much of a processor.

Now I, on the other hand, being a quite capable computer geek, manage to completely heat my house during the winter with my processor.

Just kidding (although the bit about more cpu power drawing more electrical power is basically true).

20 watts? wow. I think that my chip is 3.3 volts :slight_smile: I guess the rest of the energy is to power all the crap that’s in the case, the fans, cards, etc.

Balthisar, how do you get a Mac to work on 20 watts?

Actually EVERYTHING inside the PC is on the internal power supply.

Just becuase it’s not hooked into it like the dives are, they are. That’s one of the reasons why there are several wires from the PSU to the motherboard.

All of your PCI/ISP cards are run from power from the PSU, but the motherboard controls the output. I used to have a list of what the maximun pull was for every basic item, and you would be able to get a general idea of how much power you would use.

A suggestion though, if you’re getting a Geforce2 or 3, GET a 350 watt PSU. If you’re getting an Athalon and a Gforce2 get a 400 or higher. A 350 would work, but a 400 would make sure you have power for ANYTHING you want to add to that bad boy.

“400 would make sure you have power for ANYTHING”

You must not be in California, man, we are conserving electricity! Or trying to.

You need a 300W Power Supply with a Duron(basically the same as a Thunderbird, just slowed down a little). You may be able to get by with 250 but why risk it. Research will save you a lot of headaches. I like


For what it’s worth, you probably don’t really need a 300 watt power supply. It’s one of those things that doesn’t cost much more, and it makes sure you’re definitely going to have enough power, but despite all the warnings, even an Athlon machine whose CPU alone pulls 50W isn’t that huge.

I bought an AC power monitor which you plug electrical devices into and it reports how much power it’s using instantaneously and averaged over a long time, and my Athlon 1.2 with 5 hard drives and 6 PCI cards was using 165 Watts peak at boot time. After all the drives spun up, it was using about 125 when idle, and heavy I/O on all the disks at once brings it up to 145 (this is how much power was drawn from the wall, so due to inefficiencies in the power supply, even less was being used internally by the components).

I’ve heard a rule-of-thumb that you can expect the average PCI card to use 15W, and hard disks are about 10W each at startup. Obviously, a GeForce 3 is going to use more power, and probably a 15000 RPM hard disk would too, but it’s still a good rule of thumb. Estimate the motherboard chipset and onboard PCI devices as two extra PCI cards (a wild-ass guess), add in 50W for a Hot N Spicy Athlon and you’ve probably got a reasonable estimate of your needs.

That said, one reason to go with a bigger power supply than you think you need is that the important number isn’t really the total number of watts it’ll put out, it’s how many watts it’ll put out at each voltage level. When you really get into the nitty gritty, you’ll find that power supplies are rated based on how much power they put out on their various leads (12V, +/-5V, etc). It’s generally too much of a nuisance to add up exactly what your requirements are for each of these, so you just add 25% to your total requirements and call it a day. In the end, I bought a 300W power supply anyway because I’m just That Kind Of Nerd.

Regarding the 20W mac, it’s probably a laptop. My Toshiba averages 11W when it’s plugged into the wall.

Leave it to an anal-retentive geek to have actually measured. :slight_smile:

Weird_AL_Einstein, so what did you do?

I draw from the PC power supply to power other things which came with their own separate adapters but I just hate having all those adapters plugged in. My scanner, speakers, etc., all work at 12V so I just draw from the computer’s 12V.

Just a few days ago though, while moving stuff around, I accidentaly shorted the 12V when unplugging one of the jacks. After holding my breath for a while I sighed with relief… the power supply had shut down and nothing was damaged. It re-started without a hitch. Maybe a fuse on that output line would be a good idea anyway.

first off read:

its a good power supply primer.

second for what you have/want you might very well need something upwards of 350 - 400 watts. Better safe than sorry.

If you plan on having 3 hard drives, dvd rom or ram drives, cdrws, and so on make sure you have enough available ides. Most systems can only have 4 ide devices hooked up. When you buy the system inquire as to how many ide devices the system can accomodate. Some motherboards now come with 4 ide connectors (2 of those supporting ATA100) so you can have 8 devices. As to power suppy? I have a 300 watt and it’s enough to run 2 cd writers, a dvd rom drive, an ata100 45 gig hard drive, internal zip, floppy, 20 gig tape drive, tv tuner, agp video card, modem, 2 nics, sound card, and whatever else external stuff I use that is powered by the USB port its hooked up from. Go with 300…at least. If you try to run all the stuff I do from a 250W PS it probably won’t be as reliable, and might even fail prematurely.

Just wanted to thank everyone who has contributed to this thread. At the moment I am waiting on a response to an email I sent to the company asking a few questions about the system based on info obtained here.